1. Field of the Invention
The present invention relates to an optical recording medium and a reproducing apparatus, in particular, relates to a copy-protection type optical recording medium and the reproducing apparatus for the optical recording medium.
2. Description of the Related Art
Presently, there are widely used a read-only-type optical disc such as a CD (Compact Disc) for recording music information or a CD-ROM (Read-Only-Memory) for recording information such as a computer software and a database, an additionally-writable-type disc such as a write once (WO) disc on which information can be written only once, and an erasable-type disc such as a magneto-optical (MO) disc on which information can be repeatedly written. As well known, it can be easily performed to read out data recorded on a read-only-type optical disc and to record the data obtained therefrom, for instance, on another additionally-writable-type optical disc. Presently, there is rarely considered a measure to protect the music information, the computer software and the database recorded on the read-only-type optical disc from being copied. Therefore, an illegal copying can be easily performed on original CDs and CD-ROMs.
In recording a precious software on the read-only-type optical disc, however, there has been taken a measure to protect such precious software from illegal copying by employing a hardware key or a special data disc referred to as a key disc for the protection.
In the above method, however, it requires the hardware key or the key disc to protect the software from being illegally copied in addition to the recording medium for recording the software, which poses an increase of cost of the software and gives users a potential problem that the recording medium becomes impossible to be used upon breakage or loss of the hardware key or the key disc.
Recently, an optical disc which has more than two layers of information recording in the direction of its thickness is available, and for such an optical disc, a copy protection function is also required.